That seems an argument that some don't wish to equate into the cost of producing a paper-version of a book... transport costs, especially these days, must be significant.
Not only for the finished book itself, but starting the whole process from tree-felling/paper-recycling through to ink manufacture; factor in staff costs associated with these....

The blatant ignoring of "incidental costs" (like the impacts of pollution and costs of cleanup related to a product, service or factory) is an American tradition that is long overdue for rethinking. Paper production has heavy water usage and polluting costs that few outside the industry know about, and no one inside the industry wants to mention. If they were ever held accountable for those costs, the cost of paper would probably skyrocket...